Putting your PC into sleep mode manually or automatically can have several advantages. Technically, it is a low power mode, and sleep, suspend or stand by are all referring to the same mode.
What happens in the background is that the last state of the system is stored in RAM before power gets cut to all devices and systems that are not necessary for this minimal mode of operation.
The state is resumed when you hit the wake button, or when the keyboard or mouse are moved.
Sometimes, the computer comes out of sleep mode without you doing anything. This can have several causes, and this guide discusses several of them.
Part 1: Wake diagnosis
The first thing you should do is try and determine the source or device that is waking up your PC. Windows ships with several tools that you can use for the purpose, and this part of the guide explains how you can use them to find out more about the source.
Note that while it may reveal information to you, it is not always the case. It can happen that the diagnostic programs return no sources at all, or only unknown sources.
Still, it is a good idea to start here as a hit will provide you with the information needed to prevent that the computer wakes up automatically while in sleep mode.
Command line diagnosis
First thing you may want to do is check whether devices are responsible for waking up the computer automatically. Do the following to find that out:
- If you are using Windows 7, click on the start menu button, enter cmd, right-click cmd.exe and select Run as Administrator.
- If you are using Windows 8.x, use Windows-X to display a command menu, and select Command Prompt (Admin) from the available list.
- Type powercfg -lastwake and as a second command powercfg -devicequery wake_armed.
- Devices that are responsible for waking up the computer may be listed here.
- You may also want to run powercfg -waketimers to find out whether any wake times are configured to bring back the computer when it enters sleep mode.
- Sometimes, the name of a program may be displayed here. If that is the case, you may want to go through the applications options to figure out a way to prevent it from waking up the PC.
Windows Event Viewer diagnosis
While still on the command line, type eventvwr.msc to launch the Windows Event Viewer.
- Select Windows Logs > System from the menu in the sidebar.
- Once the log is displayed, select Filter Current Log from the Actions menu.
- A new window opens up that you use to customize what is displayed in the selected even t log.
- Locate Event sources there and select Power-Troubleshooter from the context menu. The list is sorted alphabetically, and you should not have any issues finding the filter item in the menu.
- All entries are listed by level, date and time, and Event ID.
- Open the entries closed in date and time to the waking of the PC and check for the Wake Source listing there. It may reveal what woke the computer.
Part 2: Fixing wake mode
This is the part where we apply the fix, to prevent that sleep mode is left automatically. If you have discovered what is responsible for it on your system, skip all suggestions except for the one that matches your issue.
If you do not know the particular source, try them all to find out more about it. I suggest you try one solution, put your PC into sleep mode, and see if it recovers from that automatically. If it does, that was not the solution for your issue, and you should go to the next suggested fix and try that.
Fixing the mouse
The computer mouse may be responsible for bringing the PC out of sleep mode. You can find out if that is the case, and disable the feature, in the following way:
- Tap on the Windows-key and enter mouse here.
- You should see a Control Panel entry labeled mouse if you are using Windows 7. If you are using Windows 8, type mouse, hit return, select to see all settings, and select the result that is labeled Mouse and nothing else.
- This opens the Mouse Properties on the desktop.
- Switch to the Hardware tab here and select Properties on it.
- Click on the Change settings button when the new window opens up.
- Switch to the Power Management tab here and uncheck "Allow this device to wake the computer".
Alternatively, open the Device Manager from the desktop Control Panel, locate the Mice and other pointing devices listing here, and right-click on the devices listed under it to select properties there. Or, simply double-click on the device in question.
Here you get the power management options directly, without having to go through the lengthy process described above.
Fixing Wake Timers
If a wake timer is responsible for waking your PC, you may want to check out the application that is responsible for that to prevent it from waking up your PC.
If you do not want any wake timers to be used, it is possible to disable the feature completely.
- Press the Windows-key and type powercfg.cpl to open the Power Options of the PC.
- Click on change plan settings next to the current plan, and repeat the process outlined below for all other plans that you are using.
- Click on change advanced power settings on the next page. This opens a new window that displays the advanced power options of the selected plan.
- Select Sleep > Allow wake timers, and change the setting from enable to disable by clicking on it.
- Click apply to save the changes.
Fixing network cards
Network adapters may wake the PC as well. You can check how the installed adapters are configured by running the following commands:
- Tap on the Windows-key, type device manager, and select the result from the list of suggestions.
- Select Network Adapters and double-click on the main network adapter. If you have multiple listed here, repeat the process for each that is in use.
- Switch to the Power Management tab in the new window that opens up and uncheck "Allow this device to wake the computer".
- Additionally, switch to Advanced, and locate the properties "wake on pattern match" and "wake on magic packet", and if they are enabled, disable them.
Side tip: You may also want to check your BIOS configuration for "wake on ring" and "wake on LAN" settings if available, and disable those.
Command line Fu
Here is a list of useful commands that can help you find out more about your PC's sleep mode and wake up configuration:
- powercfg -a displays a list of available sleep states of the computer.
- powercfg -devicequery wake_armed lists all devices that can wake the computer
- powercfg -devicequery wake_programmable lists all devices that can be programmed to wake up the PC.
- powercfg -devicedisablewake "exact device name" disables the wake functionality of the selected device.
- powercfg -deviceenablewake "exact device name" will enable that device again.
- powercfg -lastwake displays the last device that woke up the PC.
- powercfg -waketimers lists all active wake timers.
If you want to know more about the sleep and wake functionality, use the following resources as a starting point:
- How to make your PC wake from sleep automatically [How to Geek]
- Wake Patterns explained [Ukleja]
- Troubleshoot Vista or Windows 7 Sleep Mode Problems [Vistax64]
- Sleep Mode overview [Wikipedia]